PROJECT SUMMARY BCA2 (Breast Cancer-Associated gene 2, also known as RNF115, ZNF364 or Rabring7) is a RING-finger E3 ubiquitin ligase with anti-HIV activity. In particular, BCA2 promotes the lysosomal degradation of Gag, thereby inhibiting virion assembly (Nityanandam and Serra-Moreno, 2014). We now have evidence that BCA2 provides a regulatory negative feedback on NF-?B (Colomer-Lluch and Serra-Moreno, 2017), a pro- inflammatory cascade elicited upon infection. Remarkably, HIV-1 takes advantage of this innate cascade to ensure gene expression and genome replication by enhancing viral transcription. However, the inactivation of NF-?B is a major determinant towards the establishment of a latent infection. Currently, the latent reservoir, a group of long-lived cells carrying latent HIV-1 proviruses, represents the most critical barrier to functionally cure HIV/AIDS. Since BCA2 blocks NF-?B, we predict that this activity enforces proviral latency. We will test this hypothesis by (1) elucidating the molecular mechanism by which BCA2 modulates NF-?B, and its effects on the transcriptional capacity of HIV-1, and (2) assessing the implication of BCA2 in the establishment and maintenance of proviral latency. These studies will increase our fundamental understanding of the mechanisms involved in the establishment of proviral latency, with the ultimate goal of exploiting them to permanently disable the latent reservoir.